Encapsulated Quantum Dots in Sol-Gel and Polymer Matrices As Optical Filtering and Wavelength-Shifting Materials

Encapsulated Quantum Dots in Sol-Gel and Polymer Matrices
as Optical Filtering and Wavelength-Shifting Materials

Michael Z. Hu and Zane W. Bell

Quantum-dot nanoparticles of ZnO and CdS were chemically synthesized and then encapsulated inside a silica sol-gel monolithic solid or polymer (PMMA) matrices. The nanoparticles serve as the “guest” inside the host matrices. Nanoparticles are developed with tunable optical properties (i.e., UV-VIS absorption and photoluminecent emission). The guest-host composite optical materials were engineered to provide the task-specific absorption cutoff sharpness and peak position (for optical filtering), or alternatively, provide desirable absorption and emission peaks (for wavelength-shifting). Such developed optical materials are strategically designed for optical signal management such as for nuclear detection or other optical sensing applications. One example of optical signal management is on the discrimination of optical signals induced from neutron and gamma-ray events in a scintillating crystal.  Different detector crystals generate different optical signals that requires tunability of optical filtering or wavelength-shifting to meet the specific signal management needs. Qunatum-dot materials offer such optical tunability. However, challenges remains in the selection of composition, size and compatible encapsulation inside a solid matrix platform. Besides absorption peak position (cutoff) control, future work needs to explore the possibility of quenching of photoluminecense (for filter development) or simultaneously tuning the selective absorption and emission (for wavelength-shifter development).